[vc_empty_space][vc_empty_space]
Seismic velocity structure of the Jakarta Basin, Indonesia, using trans-dimensional Bayesian inversion of horizontal-to-vertical spectral ratios
Cipta A.a,b, Cummins P.a,c, Dettmer J.d, Saygin E., Irsyam M.f, Rudyanto A.g, Murjaya J.g
a Research School of Earth Sciences, Australian National University, Canberra, 0200, Australia
b Geological Agency of Indonesia, Bandung, Jawa Barat, 40122, Indonesia
c Geoscience Australia, Canberra, 2601, Australia
d Department of Geoscience, University of Calgary, Calgary, T2N 1N4, Canada
e The Commonwealth Scientific and Industrial Research Organisation (CSIRO), University of Western Australia, Canberra, 2601, Australia
f Faculty of Civil and Environment Engineering, Bandung Institute of Technology, Bandung, 40132, Indonesia
g Indonesian Agency for Meteorology Geophysics and Climatology, DKI, Jakarta, 10720, Indonesia
[vc_row][vc_column][vc_row_inner][vc_column_inner][vc_separator css=”.vc_custom_1624529070653{padding-top: 30px !important;padding-bottom: 30px !important;}”][/vc_column_inner][/vc_row_inner][vc_row_inner layout=”boxed”][vc_column_inner width=”3/4″ css=”.vc_custom_1624695412187{border-right-width: 1px !important;border-right-color: #dddddd !important;border-right-style: solid !important;border-radius: 1px !important;}”][vc_empty_space][megatron_heading title=”Abstract” size=”size-sm” text_align=”text-left”][vc_column_text]© The Author(s) 2018.Characterizing the interior structure of the Jakarta Basin, Indonesia, is important for the improvement of seismic hazard assessment there. A dense-portable seismic broad-band network, comprising 96 stations, has been operated between October 2013 and February 2014 covering the city of Jakarta. The seismic network sampled broad-band seismic noise mostly originating from ocean waves and anthropogenic activity. We used horizontal-to-vertical spectral ratio (HVSR) measurements of the ambient seismic noise to estimate fundamental-mode Rayleigh wave ellipticity curves, which were used to infer the seismic velocity structure of the Jakarta Basin. By mapping and modelling the spatial variation of low-frequency (0.124-0.249 Hz) HVSR peaks, this study reveals variations in the depth to the Miocene basement. These variations include a sudden change of basement depth from 500 to 1000m along N-S profile through the centre of the city, with an otherwise gentle increase in basin depth from south to north. Higher frequency (2-4 Hz) HVSR peaks appear to reflect complicated structure in the top 100m of the soil profile, possibly related to the sediment compaction and transitions among different sedimentary sequences. In order to map these velocity profiles of unknown complexity, we employ a trans-dimensional Bayesian framework for the inversion of HVSR curves for 1-D profiles of velocity and density beneath each station. Results show that very low-velocity sediments ( < 240ms-1) up to 100 m in depth cover the city in the northern to central part, where alluvial fan material is deposited. These low seismic velocities and the very thick sediments in the Jakarta Basin will potentially contribute to seismic amplification and basin resonance, especially during giant megathrust earthquakes or large earthquakes with epicentres close to Jakarta. Results have shown good correlationwith previous ambient seismic noise tomography and microtremor studies. We use the 1-D profiles to create a pseudo-3-D model of the basin structure which can be used for earthquake hazard analyses of Jakarta, a megacity in which highly variable construction practices may give rise to high vulnerability. The methodology discussed can be applied to any other populated city situated in a thick sedimentary basin.[/vc_column_text][vc_empty_space][vc_separator css=".vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}"][vc_empty_space][megatron_heading title="Author keywords" size="size-sm" text_align="text-left"][vc_column_text]Complicated structures,Earthquake hazard analysis,Horizontal-to-vertical spectral ratios,Seismic hazard assessment,Seismic noise,Seismic velocity structure,Site effects,Variable constructions[/vc_column_text][vc_empty_space][vc_separator css=".vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}"][vc_empty_space][megatron_heading title="Indexed keywords" size="size-sm" text_align="text-left"][vc_column_text]Seismic noise,Site effects,Surface waves[/vc_column_text][vc_empty_space][vc_separator css=".vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}"][vc_empty_space][megatron_heading title="Funding details" size="size-sm" text_align="text-left"][vc_column_text]Computations were performed on the Terrawulf cluster, a computational facility supported through AuScope and the Australian Geophysical Observing System (AGOS). We used geopsy software to estimate the HVSR curve, the source code can be downloaded from http://www.geopsy.org/. Most of the figures are drawn using Generic Mapping Tools (Wessel & Smith 1998), python and QGIS (QGIS Development Team). We also thank Laurence Davies for crucial advice on the use of the Wathelet[2005] code for HVSR computation. We wish to express our gratitude to Muriel Naguit for comments that helped improve the manuscript. We would like to thank Andrea Berbellini and anonymous reviewer for their insightful comments and suggestions on the manuscript that led us to improve our work. Our revisions reflect all reviewers’ suggestions and comments. This work was partially supported by Australian Department of Foreign Affairs and Trades Grant 91982 and Australian Research Council (ARC) Linkage Grant LP110100525. AC was supported by a scholarship from the Indonesian Ministry of Energy and Mineral Resources (MAK 020.01.01.1881.002.001.012 A.521219).[/vc_column_text][vc_empty_space][vc_separator css=".vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}"][vc_empty_space][megatron_heading title="DOI" size="size-sm" text_align="text-left"][vc_column_text]https://doi.org/10.1093/gji/ggy289[/vc_column_text][/vc_column_inner][vc_column_inner width=”1/4″][vc_column_text]Widget Plumx[/vc_column_text][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][/vc_column][/vc_row]